llvm dev - Jun 2013 - [LLVMdev] APFloat renaming isNormal => isFiniteNonZero and isIEEENormal => isNormal

IEEE-754R defines a normal floating point number as:
2.1.38 normal number: For a particular format, a finite non-zero floating-point
number with magnitude greater than or equal to a minimum bemin value, where b is
the radix. Normal numbers can use the full precision available in a format. In
this standard, zero is neither normal nor subnormal.

This implies that a denormal is not a normal number.

In contrast, the current implementation of isNormal in APFloat does treat
denormal numbers as normal numbers breaking this definition. This is not just a
predicate that has a name that differs from IEEE-754R (which I am fine with),
but is an actual name collision with IEEE-754R with a different semantic
meaning. This could easily lead to programmer error and thus in my humble
opinion is worth the hassle/trouble of fixing.

Does anyone have any thoughts/suggestions/objections with my renaming isNormal
=> isFiniteNonZero (and making all the relevant changes in the relevant
codebases) and isIEEENormal => isNormal?

Awaiting the flames,
Michael


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I think it’s a splendid idea (but you already knew that).

On Jun 18, 2013, at 6:45 PM, Michael Gottesman <mgottesman at apple.com>
wrote:
> IEEE-754R defines a normal floating point number as:
> 2.1.38 normal number: For a particular format, a finite non-zero
floating-point number with magnitude greater than or equal to a minimum bemin
value, where b is the radix. Normal numbers can use the full precision available
in a format. In this standard, zero is neither normal nor subnormal.
> 
> This implies that a denormal is not a normal number.
> 
> In contrast, the current implementation of isNormal in APFloat does treat
denormal numbers as normal numbers breaking this definition. This is not just a
predicate that has a name that differs from IEEE-754R (which I am fine with),
but is an actual name collision with IEEE-754R with a different semantic
meaning. This could easily lead to programmer error and thus in my humble
opinion is worth the hassle/trouble of fixing.
> 
> Does anyone have any thoughts/suggestions/objections with my renaming
isNormal => isFiniteNonZero (and making all the relevant changes in the
relevant codebases) and isIEEENormal => isNormal?
> 
> Awaiting the flames,
> Michael
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I would give you 20 thumb up if I could.

At the time I add the isDenormal() , I realized the name "isNormal()" 
need some change to reflect its real meaning,
but I was reluctant to make that change, partially because I was a big 
llvm newbie at that time.
(now, I'm just slightly smaller nut than I was :-)).

To test a real "normal" FP, I wrote the code this way "isNormal()
&&
!isDenorma()".
With your change, this condition can be simplified.

On 6/18/13 4:21 PM, Stephen Canon wrote:
> I think it's a splendid idea (but you already knew that).
>
> On Jun 18, 2013, at 6:45 PM, Michael Gottesman <mgottesman at apple.com 
> <mailto:mgottesman at apple.com>> wrote:
>
>> IEEE-754R defines a normal floating point number as:
>>
>> 2.1.38 normal number:For a particular format, a finite non-zero 
>> floating-point number with magnitude greater than or equal to a 
>> minimumbeminvalue, wherebis the radix. Normal numbers can use the 
>> full precision available in a format. In this standard, zero is 
>> neither normal nor subnormal.
>>
>> This implies that a denormal is*not* a normal number.
>>
>> In contrast, the current implementation of isNormal in 
>> APFloat* does* treat denormal numbers as normal numbers breaking this 
>> definition. This is not just a predicate that has a name that differs 
>> from IEEE-754R (which I am fine with), but is an actual name 
>> collision with IEEE-754R with a different semantic meaning. This 
>> could easily lead to programmer error and thus in my humble opinion 
>> is worth the hassle/trouble of fixing.
>>
>> Does anyone have any thoughts/suggestions/objections with my renaming 
>> isNormal => isFiniteNonZero (and making all the relevant changes in 
>> the relevant codebases) and isIEEENormal => isNormal?
>>
>> Awaiting the flames,
>> Michael
>
>
>
> _______________________________________________
> LLVM Developers mailing list
> LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
> http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev
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LGTM (and you've already gotten other positive feedback as well).

-eric

On Tue, Jun 18, 2013 at 3:45 PM, Michael Gottesman <mgottesman at
apple.com> wrote:
> IEEE-754R defines a normal floating point number as:
>
> 2.1.38 normal number: For a particular format, a finite non-zero
> floating-point number with magnitude greater than or equal to a minimum
> bemin value, where b is the radix. Normal numbers can use the full
precision
> available in a format. In this standard, zero is neither normal nor
> subnormal.
>
> This implies that a denormal is not a normal number.
>
> In contrast, the current implementation of isNormal in APFloat does treat
> denormal numbers as normal numbers breaking this definition. This is not
> just a predicate that has a name that differs from IEEE-754R (which I am
> fine with), but is an actual name collision with IEEE-754R with a different
> semantic meaning. This could easily lead to programmer error and thus in my
> humble opinion is worth the hassle/trouble of fixing.
>
> Does anyone have any thoughts/suggestions/objections with my renaming
> isNormal => isFiniteNonZero (and making all the relevant changes in the
> relevant codebases) and isIEEENormal => isNormal?
>
> Awaiting the flames,
> Michael
>
>
>
> _______________________________________________
> LLVM Developers mailing list
> LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
> http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev
>

It seems like there is a consensus that this is a good change. Any nay sayers?

Michael

On Jun 18, 2013, at 5:07 PM, Eric Christopher <echristo at gmail.com>
wrote:
> LGTM (and you've already gotten other positive feedback as well).
> 
> -eric
> 
> On Tue, Jun 18, 2013 at 3:45 PM, Michael Gottesman <mgottesman at
apple.com> wrote:
>> IEEE-754R defines a normal floating point number as:
>> 
>> 2.1.38 normal number: For a particular format, a finite non-zero
>> floating-point number with magnitude greater than or equal to a minimum
>> bemin value, where b is the radix. Normal numbers can use the full
precision
>> available in a format. In this standard, zero is neither normal nor
>> subnormal.
>> 
>> This implies that a denormal is not a normal number.
>> 
>> In contrast, the current implementation of isNormal in APFloat does
treat
>> denormal numbers as normal numbers breaking this definition. This is
not
>> just a predicate that has a name that differs from IEEE-754R (which I
am
>> fine with), but is an actual name collision with IEEE-754R with a
different
>> semantic meaning. This could easily lead to programmer error and thus
in my
>> humble opinion is worth the hassle/trouble of fixing.
>> 
>> Does anyone have any thoughts/suggestions/objections with my renaming
>> isNormal => isFiniteNonZero (and making all the relevant changes in
the
>> relevant codebases) and isIEEENormal => isNormal?
>> 
>> Awaiting the flames,
>> Michael
>> 
>> 
>> 
>> _______________________________________________
>> LLVM Developers mailing list
>> LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
>> http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev
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